Consumers use paper tissue products, such as paper towels, facial tissues and bath tissues, for a wide variety of applications. Facial tissues are not only used for nose care but, in addition to other uses, can also be used as a general wiping product. Consequently, there are many different types of tissue products currently commercially available.
In some applications, tissue products are treated with various additives, such as polysiloxane lotions in order to increase the softness of the facial tissue. Adding silicone compositions to a facial tissue can impart improved softness to the tissue while maintaining the tissue""s strength and while reducing the amount of lint produced by the tissue during use.
In the papermaking industry, various manufacturing techniques have been specifically designed to produce paper products which consumers find appealing. Manufacturers have employed various methods to apply chemical additives, such as silicone compositions, to the surface of a paper web. Currently, one method of applying chemicals to the surface of a paper web is the rotogravure printing process. A rotogravure printing process utilizes printing rollers to transfer chemicals onto a substrate. Depending upon the configuration, the rotogravure process can be a direct printing process, an indirect printing process or an offset printing process. Chemical emulsions that are applied to webs using the rotogravure printing process typically require the addition of water, surfactants, and/or solvents in order for the emulsions to be printed onto the substrate. Such additions are not only costly but also increase drying time and add process complexity.
Another method of applying chemical additives to the surface of a tissue web is spray atomization. Spray atomization is the process of combining a chemical with a pressurized gas to form small droplets that are directed onto a substrate, such as paper. One problem posed with atomization processes is that manufacturers often find it difficult to control the amount of chemical that is applied to a paper ply. Thus, a frequent problem with spray atomization techniques is that a large amount of over-spray is generated, which undesirably builds upon machinery as well as the surfaces of equipment and products in the vicinity of the spray atomizer. Furthermore, over-spray wastes the chemical being applied, and comprises a generally inefficient method of applying additives to a tissue web. Additionally, lack of control over the spray atomization technique also affects the uniformity of application to the tissue web.
In view of the above, a need exists in the industry for improving the method for application of chemical additives to the surface of a paper web. Further, when it is necessary or desired to apply an additive to both sides of a paper product, the above-described problems can become exacerbated. As such, a need also exists for a method of applying chemical additives to both sides of a paper web.
In general, the present invention is directed to an improved process for applying compositions to paper webs, such as tissue webs, paper towels and wipers. More particularly, the present invention is directed to an improved process for applying compositions to opposite sides of a paper web in a single process line. The present invention is also directed to improved paper products made from the process.
For example, in one embodiment, the present invention is directed to a process for applying an additive to a paper web, such as a tissue web, that includes the step of extruding a viscous composition onto a first side of the paper web as the paper web is wound into a roll. The viscous composition can have a viscosity sufficient for the composition to form fibers as the compositions is extruded onto the web. In general, any suitable extrusion device can be used to apply the composition to the web. In one embodiment, for instance, the composition is extruded through a melt blown die and attenuated prior to being applied to the web.
In accordance with the present invention, the web is wound under sufficient tension to cause a portion of the composition that has been applied to the first side of the web to transfer to the second side of the web during continued winding of the web. For instance, in one embodiment, at least 10% by weight of the composition can transfer to the second side of the tissue web, and particularly at least 20% by weight of the composition can transfer the second side of the tissue web. In general, the first side of the web to which the viscous composition is initially applied can be either side of the web. For instance, the first side of the web can be the side of the web facing the center of the formed roll or can be the side of the web facing away from the center of the formed roll.
As described above, the composition being extruded onto the web can be attenuated as the composition exits the die. In one embodiment, for instance, the composition can be attenuated using an airstream that contacts the composition as it is extruded from the die. Of particular advantage, the airstream can also direct the composition on to the web at a location in close proximity to where the web is being wound into a roll. For example, the composition can be applied to the web within about 30xe2x80x2 upstream of where the web is being wound into a roll, and particularly within about 15xe2x80x2 upstream of where the web is being wound into a roll.
In general, any suitable paper web can be treated in accordance with the present invention. For example, the paper web in one embodiment can be uncreped through-air dried sheet. The paper web can have a bulk density of at least 2 cc/g and can have a basis weight of from about 10 gsm to about 80 gsm. The paper web can contain bulk fibers either alone or in conjunction with synthetic fibers. Further, the web can contain thermomechanical pulp. The paper web can be made from a stratified fiber furnish or it can be made from a homogeneous fiber furnish.
The composition can generally be any material that provides benefits to paper webs. For instance, the composition can be a topical preparation that improves the physical properties of the web, that provides the web with anti-bacterial properties, that provides the web with medicinal properties, or that provides any other type of wellness benefits to a user of the paper web. For instance, the composition can contain an anti-acne agent, an anti-microbial agent, an anti-fungal agent, an antiseptic, an antioxidant, a cosmetic astringent, a drug astringent, an aiological agent, an emollient, an external analgesic, a humectant, a moisturizing agent, a skin conditioning agent, a skin exfoliating agent, a sunscreen agent, a debonder, and mixtures thereof. In one embodiment, the composition is a softener. The softener can be, for instance, a silicone, such as a polysiloxane.
Of particular advantage, the process of the present invention is well-suited to applying relatively high viscous compositions to paper webs. For instance, the composition can have a viscosity of at least 500 cps, particularly 2000 cps and more particularly can have a viscosity of at least 3000 cps. Since the process is capable of handling high viscosity compositions, various chemical additives can be added directly to a paper web without having to dilute the additive with, for instance, water or any other type of dilution agent to form a solution or emulsion.
The amount of the composition that is applied to the paper web depends on the particular application. For example, when applying a softener to a tissue web, the softener can be added in an amount from about 0.25% to about 10% by weight and particularly from about 0.5% to about 5% by weight, based upon the weight of the web. As described above, in one embodiment, the composition is extruded through a melt blown die onto the paper web. The melt blown die can have a plurality of nozzles at a die tip. The nozzles can be arranged in one or more rows along the die tip. The fibers exiting the nozzles can have a diameter of from generally about 5 microns to about 100 microns or greater.